A number of naturally occurring cyclic peptides are known in the art including echinocandin B (A30912A), aculeacin, mulundocandin, sporiofungin, L-671,329, and S31794/F1. In general, these cyclic peptides may be structurally characterized as a cyclic hexapeptide core (or nucleus) with an acylated amino group on one of the core amino acids. This acyl group is typically a fatty acid moiety forming a side chain off the nucleus. For example, echinocandin B has a linoleoyl side chain while aculeacin has a palmitoyl side chain.
These natural products have limited inherent antifungal and antiparasitic properties. The natural compounds may be structurally modified in order to enhance these properties or to improve the compound's stability and/or water solubility. Turner, W. W., Rodriguez, M. J., Cur. Pharm. Des., 2:209, 1996. For example, the fatty acid side chain may be removed from the cyclic peptide core to provide an amino nucleus which may then be re-acylated to provide semi-synthetic compounds. Furthermore, the homotyrosine moiety in the cyclic peptide may be O-glycosylated to provide further elaborated, novel, semi-synthetic compounds such as those claimed in the present application.